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Revert "sbitmap: fix io hung due to race on sbitmap_word::cleared"

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This reverts commit 681583ad67 which is
commit 72d04bdcf3f7d7e07d82f9757946f68802a7270a upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I6c645c8b4a157820561507a1cf3c1180b94aebff
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
This commit is contained in:
Greg Kroah-Hartman
2024-09-12 06:34:05 +00:00
parent 38dfa1feed
commit e3e84f6205
2 changed files with 7 additions and 34 deletions
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5
include/linux/sbitmap.h
View File

@@ -36,11 +36,6 @@ struct sbitmap_word {
* @cleared: word holding cleared bits
*/
unsigned long cleared ____cacheline_aligned_in_smp;
/**
* @swap_lock: serializes simultaneous updates of ->word and ->cleared
*/
spinlock_t swap_lock;
} ____cacheline_aligned_in_smp;
/**

36
lib/sbitmap.c
View File

@@ -60,30 +60,12 @@ static inline void update_alloc_hint_after_get(struct sbitmap *sb,
/*
* See if we have deferred clears that we can batch move
*/
static inline bool sbitmap_deferred_clear(struct sbitmap_word *map,
unsigned int depth, unsigned int alloc_hint, bool wrap)
static inline bool sbitmap_deferred_clear(struct sbitmap_word *map)
{
unsigned long mask, word_mask;
unsigned long mask;
guard(spinlock_irqsave)(&map->swap_lock);
if (!map->cleared) {
if (depth == 0)
return false;
word_mask = (~0UL) >> (BITS_PER_LONG - depth);
/*
* The current behavior is to always retry after moving
* ->cleared to word, and we change it to retry in case
* of any free bits. To avoid an infinite loop, we need
* to take wrap & alloc_hint into account, otherwise a
* soft lockup may occur.
*/
if (!wrap && alloc_hint)
word_mask &= ~((1UL << alloc_hint) - 1);
return (READ_ONCE(map->word) & word_mask) != word_mask;
}
if (!READ_ONCE(map->cleared))
return false;
/*
* First get a stable cleared mask, setting the old mask to 0.
@@ -103,7 +85,6 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
bool alloc_hint)
{
unsigned int bits_per_word;
int i;
if (shift < 0)
shift = sbitmap_calculate_shift(depth);
@@ -135,9 +116,6 @@ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
return -ENOMEM;
}
for (i = 0; i < sb->map_nr; i++)
spin_lock_init(&sb->map[i].swap_lock);
return 0;
}
EXPORT_SYMBOL_GPL(sbitmap_init_node);
@@ -148,7 +126,7 @@ void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
unsigned int i;
for (i = 0; i < sb->map_nr; i++)
sbitmap_deferred_clear(&sb->map[i], 0, 0, 0);
sbitmap_deferred_clear(&sb->map[i]);
sb->depth = depth;
sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
@@ -201,7 +179,7 @@ static int sbitmap_find_bit_in_word(struct sbitmap_word *map,
alloc_hint, wrap);
if (nr != -1)
break;
if (!sbitmap_deferred_clear(map, depth, alloc_hint, wrap))
if (!sbitmap_deferred_clear(map))
break;
} while (1);
@@ -527,7 +505,7 @@ unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags,
unsigned int map_depth = __map_depth(sb, index);
unsigned long val;
sbitmap_deferred_clear(map, 0, 0, 0);
sbitmap_deferred_clear(map);
val = READ_ONCE(map->word);
if (val == (1UL << (map_depth - 1)) - 1)
goto next;